Sea
ice in the Arctic has failed to re-form for the second consecutive winter,
raising fears that global warming may have tipped the polar regions
in to irreversible climate change far sooner than predicted.

Satellite measurements of
the area of the Arctic covered by sea ice show that for every month
this winter, the ice failed to return even to its long-term average
rate of decline. It is the second consecutive winter that the sea ice
has not managed to re-form enough to compensate for the unprecedented
melting seen during the past few summers.

Scientists are now convinced
that Arctic sea ice is showing signs of both a winter and a summer decline
that could indicate a major acceleration in its long-term rate of disappearance.
The greatest fear is that an environmental "positive feedback"
has kicked in, where global warming melts ice which in itself causes
the seas to warm still further as more sunlight is absorbed by a dark
ocean rather than being reflected by white ice.

Mark Serreze, a sea ice specialist
at the US National Snow and Ice Data Centre in Colorado, said: "In
September 2005, the Arctic sea ice cover was at its lowest extent since
satellite monitoring began in 1979, and probably the lowest in the past
100 years. While we can't be certain, it looks like 2006 will be more
of the same," Dr Serreze said.

"Unless conditions turn
colder, we may be headed for another year of big sea ice losses, rivalling
or perhaps even exceeding what we saw in September 2005. We are of course
monitoring the situation closely ... Coupled with recent findings from
Nasa that the Greenland ice sheet may be near a tipping point, it's
pretty clear that the Arctic is starting to respond to global warming,"
he added.

Although sea levels are not
affected by melting sea ice - which floats on the ocean - the Arctic
ice cover is thought to be a key moderator of the northern hemisphere's
climate. It helps to stabilise the massive land glaciers and ice sheets
of Greenland which have the capacity to raise sea levels dramatically.

Dr Serreze said that some
parts of the northern hemisphere experienced very low temperatures this
winter, but the Arctic was much warmer than normal. "Even in January,
when there were actually record low temperatures in Alaska and parts
of Russia, it was still very warm over the Arctic Ocean," he said.

"The sea ice cover waxes
and wanes with the seasons. It partly melts in spring and summer, then
grows back in autumn and winter. It has not recovered well this past
winter - ice extent for every month since September 2005 has been far
below average. And it's been so warm in the Arctic that the ice that
has grown this winter is probably rather thin," he explained.

Professor Peter Wadhams,
of Cambridge University, who was the first Briton to monitor Arctic
sea ice from nuclear submarines, said: "One of the big changes
this winter is that a large area of the Barents Sea has remained ice-free
for the first time. This is part of Europe's 'back yard'. Climate models
did predict a retreat of sea ice in the Barents Sea but not for a few
decades yet, so it is a sign that the changes that were predicted are
indeed happening, but much faster than predicted."

Sea ice in the Arctic has
failed to re-form for the second consecutive winter, raising fears that
global warming may have tipped the polar regions in to irreversible
climate change far sooner than predicted.

Satellite measurements of
the area of the Arctic covered by sea ice show that for every month
this winter, the ice failed to return even to its long-term average
rate of decline. It is the second consecutive winter that the sea ice
has not managed to re-form enough to compensate for the unprecedented
melting seen during the past few summers.

Scientists are now convinced
that Arctic sea ice is showing signs of both a winter and a summer decline
that could indicate a major acceleration in its long-term rate of disappearance.
The greatest fear is that an environmental "positive feedback"
has kicked in, where global warming melts ice which in itself causes
the seas to warm still further as more sunlight is absorbed by a dark
ocean rather than being reflected by white ice.

Mark Serreze, a sea ice specialist
at the US National Snow and Ice Data Centre in Colorado, said: "In
September 2005, the Arctic sea ice cover was at its lowest extent since
satellite monitoring began in 1979, and probably the lowest in the past
100 years. While we can't be certain, it looks like 2006 will be more
of the same," Dr Serreze said.

"Unless conditions turn
colder, we may be headed for another year of big sea ice losses, rivalling
or perhaps even exceeding what we saw in September 2005. We are of course
monitoring the situation closely ... Coupled with recent findings from
Nasa that the Greenland ice sheet may be near a tipping point, it's
pretty clear that the Arctic is starting to respond to global warming,"
he added.
Although sea levels are not affected by melting sea ice - which floats
on the ocean - the Arctic ice cover is thought to be a key moderator
of the northern hemisphere's climate. It helps to stabilise the massive
land glaciers and ice sheets of Greenland which have the capacity to
raise sea levels dramatically.

Dr Serreze said that some
parts of the northern hemisphere experienced very low temperatures this
winter, but the Arctic was much warmer than normal. "Even in January,
when there were actually record low temperatures in Alaska and parts
of Russia, it was still very warm over the Arctic Ocean," he said.

"The sea ice cover waxes
and wanes with the seasons. It partly melts in spring and summer, then
grows back in autumn and winter. It has not recovered well this past
winter - ice extent for every month since September 2005 has been far
below average. And it's been so warm in the Arctic that the ice that
has grown this winter is probably rather thin," he explained.

Professor Peter Wadhams,
of Cambridge University, who was the first Briton to monitor Arctic
sea ice from nuclear submarines, said: "One of the big changes
this winter is that a large area of the Barents Sea has remained ice-free
for the first time. This is part of Europe's 'back yard'. Climate models
did predict a retreat of sea ice in the Barents Sea but not for a few
decades yet, so it is a sign that the changes that were predicted are
indeed happening, but much faster than predicted."